Method and apparatus for the reduction of NOx generation during coal dust combustion

Abstract

A burner for the combustion of coal dust in which a stream of primary air and coal dust mixture is conducted through a dust conduit connected to a primary dust tube. A secondary air tube surrounds the primary dust tube, and a tertiary air tube surrounds the secondary air tube. The secondary and tertiary air tubes are connected to a helically-shaped input housing, and a conically flared section extends from each of the secondary and tertiary air tubes. An angular momentum is applied in the dust conduit divides the primary air and coal dust mixture into high-dust and low-dust partial streams, so that the high-dust partial stream flows through the primary dust tube, and the low-dust partial stream flows through the primary gas tube.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A burner for the combustion of coal dust comprising: a dust conduit conducting a stream of a primary air and coal dust mixture; a primary dust tube connected to said dust conduit; a secondary air tube conducting secondary air and surrounding said primary dust tube; a tertiary air tube conducting tertiary air and surrounding said secondary air tube; a helically-shaped, input housing connected to said secondary air tube and said tertiary air tube; means for applying angular momentum in said secondary air tube and in said tertiary air tube; a conically flared section extending from each of said secondary air tube and said tertiary air tube; a stabilization ring at an exit end of said primary dust tube; a primary gas tube surrounded by said secondary air tube and defining an annular channel surrounding said primary dust tube, said primary gas tube conducting a primary gas; means for applying angular momentum in said dust conduit; a dip tube spaced from said angular momentum applying means in said dust conduit; a conduit line connected to said dip tube; said helically-shaped input housing connected to said conduit line and to said primary gas tube; said angular momentum applying means in said dust conduit dividing said stream of a primary air and coal dust mixture into a high-dust partial stream and into a low-dust partial stream, said high-dust partial stream, flowing through said primary dust tube, and said low-dust partial stream flowing through said primary gas tube. 
     
     
       2. A burner as defined in claim 1, wherein said coal dust has an ignition region, said coal dust conducted by said dust conduit influencing formation of NO x  in said ignition phase region so as to reduce production of NO x , said primary gas having an oxygen content, said coal dust having volatile components requiring an amount of oxygen for combustion, said ignition phase having a mean ratio of said oxygen content to said amount of oxygen required for combustion of the volatile components, said mean ratio being reduced from a given value by means for reducing said oxygen content so as to increase the coal dust content in said primary gas. 
     
     
       3. A burner for the combustion of coal dust comprising: a dust conduit conducting a stream of a primary air and coal dust mixture; a primary dust tube connected to said dust conduit, a secondary air tube conducting secondary air and surrounding said primary dust tube; a tertiary air tube conducting tertiary air and surrounding said secondary air tube; a helically-shaped input housing connected to said secondary air tube and said tertiary air tube; means for applying angular momentum in said secondary air tube and in said tertiary air tube; a conically flared section extending from each of said secondary air tube and said tertiary air tube; a stabilization ring at an exit end of said primary dust tube; a core air pip surrounded by said primary dust tube; a gas pipe surrounded by said primary dust tube, said gas pipe conducting a combustible gas and surrounding said core air pipe; said gas pipe being spaced from said core air pipe by an annular gap; and, said gas pipe having an exit end, a nozzle plate with gas exit nozzles being disposed at said exit end of said gas pipe. 
     
     
       4. A burner as defined in claim 3, wherein said burner has an ignition region, a primary gas being generated in said ignition region with combustible volatile components emitted from said coal dust through burning of said coal dust, said ignition region having a mean ratio of oxygen in said primary air and coal dust mixture to an amount of oxygen required for combustion of said volatile components, said combustible gas conducted by said gas pipe being injected into said ignition region to increase said amount of oxygen required for combustion of said volatile components and thereby lower said mean ratio and reduce NO x  formation.